The present invention relates generally to optical disc apparatuses. More particularly, the invention relates to an optical disc apparatus adoptable for compact discs (CDs), digital versatile discs (DVDs), Blu-ray discs (BDs), and the like, and having a vibration insulator for preventing signal read/write errors from occurring during recording and reproduction.
Conventional optical disc apparatuses have some vibration insulator for preventing signal read/write errors from occurring during recording and reproduction.
For example, the types of vibration insulators employed in optical disc apparatuses for CDs, DVDs, or the like, include one in which the guide shafts themselves and support sections for supporting the guide shafts are each formed of resin.
A main guide shaft and a subsidiary guide shaft exist as the guide shafts that are main constituent elements of an optical disc apparatus. In conventional types of optical disc apparatuses, for reasons of the moving stroke of an optical pickup, both the main guide shaft and the subsidiary guide shaft are typically of the same length. In addition, in terms of cost, the main guide shaft and the subsidiary guide shaft are usually made of the same metallic material and both are usually formed into the same shaft shape.
In recent years, high positioning accuracy has been required for optical disc apparatuses of high recording capacity, such as Blu-ray disc apparatuses. These optical disc apparatuses, compared with conventional ones, are required to have high positioning accuracy particularly in a focusing direction and in a tracking direction.
For example, Japanese Patent Laid-open No. 2000-311366 concerned with this technical field discloses a technique for constructing an optical disc apparatus including first and second bearings supported by a main guide shaft, and a third bearing supported by a subsidiary guide shaft; wherein a supporting point of the third bearing is disposed on a straight line which connects a midpoint on a line segment between supporting points of the first and second bearings and a center of gravity of a sliding base including an optical pickup.
For the conventional optical disc apparatus described above in the “Background of the Invention”, however, the disclosure of the technique in Japanese Patent Laid-open No. 2000-311366, for example, does not contain information on a method of preventing or controlling the vibration of the optical pickup or the vibrational resonance of the guide shafts. There has been, therefore, a problem in that the technique alone does not suffice to obtain a sufficient vibration-insulating effect.
Despite the fact that as described above, compared with that of the conventional optical disc apparatuses, high positioning accuracy in the focusing direction and in the tracking direction is required particularly for optical disc apparatuses of high recording capacity, such as Blu-ray disc apparatuses, effective measures for preventing or controlling the vibrational resonance of the main guide shaft and the subsidiary guide shaft have not been taken in conventional techniques.
More specifically, for the conventional optical disc apparatuses, both the main guide shaft and the subsidiary guide shaft are set to the same length for reasons of the stroke of the optical pickup which moves between the inner and outer peripheral edges of a disc. In addition, in terms of cost, the main guide shaft and the subsidiary guide shaft are made of the same metallic material and both are formed into the same shaft shape. Hence, during information recording on or reproduction from the optical disc, that is, during movement of the sliding base itself, the natural frequency of the main guide shaft system including the optical pickup, and the natural frequency of the subsidiary guide shaft system take the same value, for which reason, vibrational resonance occurs between the main guide shaft system and the subsidiary guide shaft. This problem, in turn, causes a further problem in that the vibrational characteristics of the optical pickup in the focusing direction deteriorate under the conditions of those frequencies, and these problems are becoming increasingly prominent in recent years.